Oil well tubing having noncommunicating fluid passages



Jan. 13, 1970 w. F. McCLURE 3, 9, 38

OIL WELL TUBING HAVING NONCOMMUNICATING FLUID PASSAGES Filed April 8,1968 INVENTOR.

WILLIAM F. MC CLURE ATTORN W United States Patent US. Cl. 285-133 9Claims ABSTRACT OF THE DISCLOSURE A length of well tubing includes aninner pipe and an outer pipe spaced about the inner pipe to define anouter fluid passage between the pipes. The pipes at one axial endinclude axially extending first threaded portions, and at the otheraxial end include axially extending second threaded portions ofcomplementary shape to the first threaded portions. First and secondcollars positioned at opposite ends of the inner pipe, fixedy connectthe pipes. Each collar includes at least one collar passage extendingaxially of the collar in fluid communication with the adjacent outerpassage. When adjacent tubing lengths are threadedly connected with theinner pipes in fluid communication, the adjacent collars are axiallyspaced to provide a peripheral passage placing the outer fluid passagesof adjacent connected tubing lengths in fluid communication.

Background of invention This invention relates to oil well tubing havingnoncommunicating fluid passages extending along the tubing, and to amethod of manufacture for such tubing.

In performing oil field operations, it is sometimes necessary to utilizesome form of a fluid actuated, downhole tool interposed in a string ofoil well tubing disposed in an oil well bore. Some types of downholetool cannot be actuated by the usual gas or liquid passing through thetubing string, but instead require the provision of special sources offluid power such as compressed air, or hydraulic liquid. For thispurpose a tool supply fluid conduit (of rigid or flexible construction)may sometimes be provided extending from the surface to the downholetool, positioned either internally or externally of the tubing string.However, with the fluid conduit in such an exposed position, problemsmay arise due to the extreme vulnerability of the conduit to damage bothfrom blows and to abrasion by drilling or producing fluids. In additionit is often necessary to rotate the string of oil well tubing whichcannot be done when an external tool supply conduit is affixed to theoutside of the tubing string.

In an attempt therefore to avoid these problems, it has been previouslyproposed to utilize double walled lengths of well tubing (provided byspaced concentric pipes) with a tool supply passage between the pipes.Adjacent tubing lengths are connected together by threaded engagementbetween one pair of threaded pipes in the tubing lengths, with theadjacent other pipes concurrently entering into sliding or abuttingengagement.

Although such prior structure may sometimes be satisfactory, certainsignificant disadvantages may be encountered for a number of reasons.For example, with the prior structure described, the slidingly connectedpipes are incapable of direct transmission of torque and tensile loadbetween adjacent tubing lengths, thus reducing the torque capacity ofthe tubing string.

Additionally such prior structures commonly used relatively small orsheet metal spacers to support the pipes in spaced relation, with thedisadvantage that under heavy torque loads, the spacers might tend tobecome sheared or otherwise distorted. Even minor distortion may be3,489,438 Patented Jan. 13, 1970 suflicient to cause some leakagebetween the inner and outer pipes, which could allow some of the liquidwithin the inner pipe (which may be drilling or production fluid) to mixwith the clean actuating fluid used for the downhole tube with possibledisastrous results. Furthermore, major distortion at the joint couldlead to complete failure of the pipe string under heavy load.

Other problems may arise in the manufacture of lengths of well tubing ofthe type described in that it may be necessary to provide complicatedjigging for maintaining the inner pipe in centralized relation to theouter pipe while the supporting spacers are Welded into' position. Inaddition, the welding process may be difiicult to carry out in view ofthe restricted accessibility existing within the annulus defined by theinner and outer pipes.

Summary of invention It is therefore a general object of the inventionto provide oil well tubing having noncommunicating fluid passages, whichobviates or minimizes problems of the type previously noted.

It is a particular object of the invention to provide a length of oilwell tubing having noncommunicating fluid passages, so designed as topermit a particularly rigid and rugged joint to be provided betweenadjacent tubing lengths.

It is another object of the invention to provide a pipe string of thetype comprising plural lengths of tubing connected end to end with eachlength formed of spaced inner and outer pipes, wherein the torque andtensile carrying capacity of both pipes in each tubing length may befully utilized.

It is a further object to provide oil well tubing for conducting twodifferent media along different noncommunicating passages in which thepossibility of admixture of the fluids at junctions between adjacenttubing lengths is obviated or minimized.

An additional object of the invention is to provide a method ofmanufacture of a pipe string of the type described which method may beperformed in a simple and convenient manner and at a low cost.

A length of well tubing according to a preferred embodiment of theinvention, intended to accomplish at least some of the foregoing objectsincludes an inner pipe having axially opposite first and second ends. Anouter pipe is spaced concentrically about the inner pipe with the pipesdefining an outer fluid passage between them. First and second annularcollars positioned adjacent the first and second ends of the inner piperespectively, extend transversely and peripherally of the outer passageand fixedly connect the pipes together. Each'collar includes at collarsfurther includes a peripherally extending, radial end surface facingaxially outwardly of'the inner pipe and intersecting the adjacent collarpassage. Abutment.

means are connected with at least one of the pipes adjacent its oppositeaxial ends. When one end of the tubing length is threadedly connected toan opposite end of another identical length of the tubing, the abutmentmeans maintains the adjacent collar radial end surfaces in sufficient,axially spaced relation to define a peripheral passage placing the outerpassages of the connected lengths of tubing in fluid communication. Inthis way continuous,

noncommunicating inner and outer passages are provided through thejunctions between adjacent tubing lengths.

Additionally, each of the collars extends axially inwardly of the pipesto a point beyond the adjacent threaded portions, to provideparticularly rigid supporting structure at the junction between adjacentlengths of well tubing.

In a further aspect of the invention, first seal means are connectedwith the threaded portions of the inner pipe to prevent leakage of thefluid between adjacent inner pipes of the connected tube lengths.Similarly, second seal means are connected with the threaded portions ofthe outer pipes to prevent leakage of fluid outwardly between theadjacent outer pipes of the connected tube lengths.

To assist ease of connection of adjacent lengths of well tubing, thefirst threaded portions are shaped to provide an axially recessed,internally threaded female socket of generally frustoconicalconfiguration with the axially extending second threaded portionsproviding an axially projecting, male connector of complementaryconfiguration to the female socket.

A method aspect of the invention is intended to provide a length of oilwell tubing having noncommunicating fluid passages. The method includesa step of providing an inner pipe with radially projecting peripheralcollars adjacent each of its end. At least one groove is formed in eachcollar extending entirely axially therethrough. An outer pipe is thensleeved over the inner pipe at one axial end of the pipes with the innerpipe projecting beyond the outer pipe at the other axial end. The oneend of the length of tubing is then provided with an internally threadedaxially recessed female socket while the other end of the tubing isprovided with an externally threaded male connector of complementaryconfiguration to the female socket.

The drawings A length of oil well tubing constructed in accordance witha preferred embodiment of the invention is illustrated in theaccompanying drawings in which:

FIGURE 1 is a side view of a tubing string formed from a plurality oflengths of well tubing according to the preferred embodiment;

FIGURE 2 is an exploded perspective view of a junction between twoadjacent lengths of the well tubing shown in FIGURE 1;

FIGURE 3 is a cross sectional, side view through a portion of thejunction between two adjacent lengths of well tubing taken on the line33 of FIGURE 4;

FIGURE 4 is a cross sectional top view of the joint between two adjacentlengths of tubing shown in FIG- URE 3 taken along the lines 44 therein,but with a full peripheral section of the tubing shown; and

FIGURE 5 is a cross sectional top view of the tubing joint shown inFIGURE 3 taken along the lines 55 therein, but with a full peripheralsection of the lengths of tubing shown.

Detailed description Referring to FIGURE 1 of the drawings, a tubingstring formed of a plurality of lengths of tubing 2 according to apreferred embodiment of the invention, is there shown. Typically thetubing string may be installed in a well bore with an upper end of thetubing string above ground level and with a fluid actuated downhole tool(not shown but comprising, for example, a safety valve) positionedseveral hundred feet down the well bore. The present invention isintended to provide a fluid path for the fluid to actuate the downholetool, which is separate from and does not communicate with the maincentral annulus of the tubing string through which drilling mud and thelike passes.

For this purpose each of the lengths of tubing 2 comprises spacedconcentric inner and outer pipes 4 and 6 respectively, defining anannular outer passage 7 between the pipes. At the upper end of thetubing string a transverse port 8 in the outer pipe 6 of one of thetubing lengths 2 above the ground, is provided for the admission ofactuating fluid to the outer passage 7. At the lower end of the tubingstring a port 9 in the inner pipe 4 of another of the lengths 2 of thetubing is provided, for delivering the actuating fluid to the tool. Ofparticular interest in the context of the present invention is thestructure provided at the junction between adjacent tubing lengths toSimultaneously connect them and provide a fluid path between theadjacent outer passages.

Each length of tubing 2 (FIGURES 2 and 3) as previously mentionedincludes one of the inner pipes 4 which is of uniform external andinternal diameter. Each inner pipe 4 is provided with a first or uppercollar 10 at its upper end, and a lower or second collar 12 at its lowerend. The upper collar 10 projects axially upwardly of the upper end ofthe inner pipe 4 and the lower collar 12 has its lower end spaced abovethe lower end of the inner pipe 4. The collars 10 and 12 which areannular, extend completely about the inner pipe 4 and are fixedlysecured thereto, extending radially across the outer passage 7. Thecollars 10 and 12 may be formed in any conventional manner such as byforging them integrally upon the pipe ends, or by securing an externallyapplied collar to the inner piepe by welding, press fitting, heatshrinking or the like, with subsequent machining of the exterior of thecollars to a uniform external diameter.

Each of the collars 10 and 12 is provided with four equally spaced,groove-like, collar passages 14 extending axially the full length of thecollar. The collar passage 14 (FIGURE 4) are preferably produced by amilling cutter and the number of them may be varied as desired. However,in general the aggregate radial cross sectional area of the grooves 14comprises only a minor portion of the total radial area of the collar onwhich the grooves are formed. Portions of the collar extendingperipherally between adjacent collar passages 14 comprises collarsegments which reinforce the outer pipe against inward collapse adjacentthe joint. Preferably these segments each extend for almost a quarter ofthe periphery of the pipe.

The previously mentioned outer pipe 6 of each length 2 of tubing ismaintained in fixed spaced relation about the associated inner pipe 4 byheat shrinking the outer pipe 6 onto the upper and lower collar 10 and12, to form a tight fit therewith, resisting both axial and rotationaldisplacement. Each outer pipe 6 at its upper end extends axiallyupwardly beyond the adjacent upper collar 10 and at its lower end, isspaced upwardly above the lower extremity of the adjacent lower collar12. The collar passages 14 in the upper and lower collars 10 and 12 arein fluid communication with the outer passage 7 at the upper and lowerextremities thereof.

To facilitate threaded connection between adjacent lengths 2 of thetubing, each tubing length 2 at its upper end includes a threaded femalesocket. The socket is provided by axially extending, upwardly diverging,upper and lower, first internally threaded portions 20a and 2012 (FIGURE3) formed on the upper collar 10 and upper internal portion of the outerpipe 6, respectively. The lower, first threaded ortion 20a on the collar10 extends from a point adjacent the upper extremity of the associatedinner pipe 4 upwardly and outwardly to the upper extremity of the collar10. The upper, first threaded portion 20b on the outer pipe 6 extendsfrom a position generally on a level with the upper extremity of thecollar 10, spaced radially outwardly therefrom, to a position adjacentthe upper extremity of the outer pipe 6. The threaded portions 20a and20b are of generally equal length and similar thread characteristics todefine the threaded female socket.

At its lower end each of the lengths 2 of tubing is provided with athreaded male connector, complementary to the female socket on the nextadjacent length of tubing 2. Such male connector is defined by a lower,second externally threaded portion 22a provided on the lower collar 12and adjacent portions of the inner pipe 4, and an upper, secondexternally threaded portion 2217 provided on the outer pipe 6. Thethreaded portions 22a and 22b are generally coextensive with anconfigured to separately, threadedly engage the respective firstthreaded portions 20a and 20b in complementary relation.

It will be understood that tubing lengths 2 may readily be connectedtogether by threadedly engaging the male connector at the lower end ofone tubing length with the female socket at the upper end of the nextsucceeding length of tubing. The inclined relation of the variousthreaded portions assists in rapid centralizing and threading of tubinglengths together.

Significantly the separate threaded connection between adjacent innerpipes afforded by the threaded portions 20a and 22a, and the separateconnection between adjacent outer pipes afforded by the threadedportions 20b and 22b, permits both the inner and outer pipes toseparately and directly transmit torque through the junction betweenadjacent tubing lengths. In this manner the combined torque carryingcapacity of both the inner and the outer pipes may be fully utilized.

It will further be appreciated that threaded connection of adjacentlengths of tubing in the manner described, places the central innerpassages of the adjacent inner pipes 4 in fluid communication. Provisionis :also made for concurrently placing the outer passages 7 of adjacentlengths of tubing 2, in fluid communication through the joint betweenadjacent tubing lengths.

For this purpose the collars 10 and 12 are provided with radiallyextending end faces 24 and 26 (FIGURE 3) respectively, each of whichfaces axially outwardly of its associated length of tubing 2 and ispositioned generally axially intermediate of the associated first andsecond threaded portions. Each of the radial end faces 24 and 26intersects the adjacent previously mentioned collar passages 14.

To maintain the radial end surfaces 24 and 26 of connected lengths oftubing 2 in spaced opposed relation on opposite sides of a radial planex-x for a purpose to be described, abutment means are provided adjacentthe axial extremities of the previously mentioned threaded portions. Theabutment means includes a first pair of downwardly and radially inwardlyinclined, mating abutting surfaces 26 and 27 at the lower extremity ofthe previously mentioned lower, first and second threaded portions 20aand 22a respectively. A second pair of matingly configured abuttingsurfaces 30 and 32 is provided at the upper extremities of the threadedportions 20b and 22b despectively. The pairs of abutting surfaces 26, 27and 30, 32 move into abutting contact to limit further threadedengagement of adjacent tubing lengths to maintain the adjacent radialend faces 24 and 26 of the collars on the connected tubing lengths inaxially spaced relation. Significantly, these mating faces also form ametal-to-metal seal.

Thus, the axially spaced, adjacent end faces 24 and 26, together withadjacent peripherally extending portions of the collars and pipes,provide a peripherally extending passage 33 (FIGURE 5) communicatingwith the various collar passages 14 in the adjacent collars 10 and 12.The peripheral passage 33 completes a continuous fluid passage betweenthe outer fluid passage 7 in one tubing length and the outer passage 7in the adjacent tubing length, through the respective collar passages14, even though the passages 14 in the adjacent collars may not beaxially aligned at the time threaded engagement of the lengths of tubingis completed. In this manner, noncommunicating inner and outer fluidpassages are simultaneously provided through connected lengths 2 oftubing merely by threadedly engaging the adjacent lengths.

In order to prevent the possibility of admixture of the fluids in theinner and outer passages along and between adjacent threads, acompressible annular seal ring 34, of the O-ring type, is interposedbetween the previously mentioned first pair of abutment surfaces 26 and27, partially received within a peripherally extending groove 35provided in the abutment surface 27. A similar annular compressible sealring 36 is mounted between the second pair of abutment surfaces 30 and32, partially received within a peripherally extending recess 38provided in the abutment surface 32. It will be appreciated that theseal rings 32 and 36 preserve the fluid-tight nature of the adjacentouter passages 7 to prevent radial leakage of any of the actuating fluidfrom the outer passages, and to prevent ingress of fluid from theinterior of the pipes that might otherwise contaminate the actuatingfluid in the outer passages.

In another important aspect of the invention, each of the collars 10 and12 extends axially inwardly of its associated length of tubing 2 beyondthe adjacent threaded portions. Thus the upper collar 12 extendsupwardly beyond the upper extremity of the associated upper, secondthreaded portion 22b while the lower collar 10 extends downwardly beyondthe lower extremity of the associated lower, first threaded portion 20a-In this manner considerable reinforcement is" provided for both lengths2 of tubing at their junction, by the collars extending axially in bothdirections beyond the junction. This added rigidity provides a valuablemargin of safety and significantly reduces the possibility of pipefailure at the junction.

A method of manufacture of a length of tubing of the type described,includes an initial step of providing a length of the inner pipe. Theinner pipe is then provided at its opposed axial extremities with theradially projecting collars. This step may be performed by heating andupsetting the pipe to provide integral collars on the pipe.Alternatively, each separate collar may be fixedly secured to the pipeends by welding, threading, press fitting or other well known methods.The axially extending collar passages are then cut in each of thecollars extending en tirely axially through the collars. The outer pipehaving an internal diameter slightly less than that of the collars isexpanding by heating, and in an expanded condition sleeved over theinner pipe, with the outer pipe projecting beyond the inner pipe at oneend and with the inner pipe projecting beyond the outer pipe at theother end. The outer pipe is cooled to heat shrink it in fixed positionabout the collars. An internally threaded female socket is then formedon the pipes at the one end and an externally threaded male connectorformed on the pipes at the other end.

Although the invention has thus far been described for use in supplyingactuating fluid, it will be appreciated that it is suited for use inother applications involving noncommunicating fluid paths, such as forexample coring operations. Additionally, the invention may be utilizedin above ground piping applications including oil field applications aswell as applications entirely outside the oil field environment. Inaddition, circulation of fluid in the outer passage may occur in bothupward and downward directions.

Summary of advantages In utilizing the method and apparatus of thepresent invention, it will be appreciated that certain significantadvantages are provided.

In particular the provision of the peripherally extending collarsbetween the concentric inner and outer pipes, provides for particularlyrigid joint construction adjacent the junction between adjacent lengthsof tubing.

In this respect, the manner in which the collars extend axially to apoint beyond the adjacent threaded portions 7 of the pipes providesmassive reinforcement for the lengths of tubing at the joints.

Also significant is the provision of a peripheral fluid passage forproviding a fluid path between collar passages in adjacent connectedtubing lengths, even when the collar passages are not axially alignedafter connection.

Of great importance is the fact that the construction described permitsthe tubing string to be rotated, as is frequently required in oil fieldoperations, without posing any possible interference to the supply ofactuating fluid to the downhole tool.

Other advantages are provided by the seals between the inner pipes andthe seals between the outer pipes, which safeguard the fluid tightintegrity of the communicating outer passages.

Also significant is the method of manufacture utilizing an outer tubeheat sleeved over an inner pipe provided with collars to provide aninterference fit therewith. This simple method of manufacture eliminatesthe need for complicated jigging or diflicult welding procedures inconnecting the pipes in spaced concentric relation.

Although the invention has been described with reference to onepreferred embodiment, it will be appreciated by those skilled in the artthat numerous additions, deletions, modifications, substitutions, andother changes not specifically described for the preferred embodimentmay be made.

What is claimed is:

1. A length of Well tubing comprising:

(a) an inner pipe,

(b) an outer pipe spaced concentrically about said inner pipe,

(c) said pipes defining an outer fluid passage between said pipes; firstand second annular collars positioned adjacent first and second axiallyopposed ends of said inner pipe respectively, said collars extendingtransversely of said outer passage fixedly connecting said pipes, eachsaid collar further including,

at least one collar passage extending entirely axially of said collar, aperipherally extending, outwardly facing, radial end surface; said firstcollar and both of said inner and outer pipes adjacent said first axialend further including, axially extending first threaded portions; saidsecond collar and both of said inner and outer pipes adjacent saidsecond axial end including,

axially extending second threaded portions shaped to be complimentary tothe respective said first threaded portions; abutment means connectedwith at least one of said pipes adjacent opposite axial ends thereof,said abutment means upon threaded connection of the length of tubing toanother, similar length of tubing causing the adjacent collar radial endsurfaces to be spaced-sufficiently apart to define -a peripheral fluidpassage communicating with the adjacent collar passages of the lengthsof tubing; and said first and said second axially extending threadedportions, upon threaded connection of said length of tubing withcomplimentary threaded portions of another length of said tubing, caus-.

ing said outer pipe of said length to be in direct torque transmittingrelationship with the outer pipe of said other length of tubing and saidinner pipe of said length to be in direct torque transmittingrelationship with the inner pipe of said other length of tubing.

2. A length of well tubing as defined in claim 1, wherein said abutmentmeans includes,

inclined, nonthreaded, axially extending first and second pairs ofmating abutment surfaces on said threaded portions of said inner andouter pipes respectively for limiting axial approaching motion ofadjacent said collar radial end faces of connected tubing lengths duringthreading engagement thereof.

3. A length of well tubing as defined in claim 2 further including,

first seal means interposed between and connected with the adjacentmating abutment surfaces of said first pairs thereof for providing aseal between adjacent said inner pipes of connected lengths of welltubing to prevent leakage of fluid from said inner pipes, and

second seal means interposed between and connected with the adjacentmating abutmentsurfaces of said second pair thereof for providing a sealbetween adjacent said outer pipes of connected lengths of well tubing toprevent leakage from said outer passages.

4. A length of well tubing as defined in claim 2 wherein:

each of said collars extends axially inwardly of said pipe to a pointspaced remotely from the adjacent threaded portions.

5. A length of well tubing as defined in claim 4 wherein,

said first threaded portions are configured to provide an axiallyrecessed, internally threaded, female socket of generally frustoconicalshape; and

said second threaded portions are configured to provide an externallythreaded male connector of complementary configuration to said femalesocket.

6. A length of wall tubing as defined in claim 1 wherein each collarincludes,

a plurality of said collar passages,

a plurality of collar segments extending peripherally between adjacentcollar passages in contiguous abutting contact with said outer pipe,said collar segments being of substantially greater peripheral extentthan said collar passages to reinforce said outer pipe againsttransverse collapse.

7. A length of well tubing according to claim 1 further including:

an axially extending outer surface formed on each side first and saidsecond annular collars; and

said at least one collar passage comprising a groove formed on saidaxially extending outer surface.

8. A pipe string providing noncommunicating axially extending fluidpassages, the pipe string comprising:

at least two lengths of well tubing disposed in end-toend relationextending axially on opposite sides of a radial plane, each said tubinglength including,

an inner pipe, an outer pipe spaced concentrically about said innerpipe, said pipes defining,

an outer fluid passage between said pipes; one of said tubing lengthsincluding,

axially extending threaded portions on each of the associated said innerand outer pipes adjacent said radial plane; the other of said tubinglengths including,

axially extending threaded portions on each of the associated said innerand outer pipes threadedly engaged with the corresponding said threadedportions of said one tubing length to fixedly connect said tubinglengths in engaged relation with said inner pipes thereof in fluidcommunication; with said inner pipes of said two lengths of tubing indirect torque transmitting relationship and said outer pipes of said twolengths of tubing in direct torque transmitting relationship; each saidtubing length further including,

at least one annular collar fixedly connected to said inner and outerpipes extending across said outer passage adjacent said radial plane,

said collar including,

a peripherally extending, outwardly facing radial end surface,

a collar passage extending entirely axially of said collar in fluidcommunication with said outer passage;

abutment means connecting with at least one of said pipes in each tubinglength adjacent opposite axial ends thereof, said abutment means ofadjacent tubing lengths being in abutting contact to cause the adjacentcollar radial end surfaces to be spaced sufliciently apart to define aperipheral fluid passage communicating with the adjacent collar passagesof the length of tubing. 9. A pipe string as defined in claim -8 furtherincluding, first seal means connected with said threaded engagingportions of said inner pipes of said tubing lengths for preventingradial leakage between adjacent said inner pipes; and second sealingmeans connected with said threaded engaging portions on said outer pipesof said tubing lengths to prevent radial leakage of fluid betweenadjacent said outer pipes.

References Cited UNITED STATES PATENTS 12/ 1924 Steele.

6/ 1932 Edmunds. 5/1933 Ricker et al. 1/1950 Frost et al. 285133 9/1958Grable 175-215 X 8/1966 Yarbrough 175-215 X 10/1966 Becker et al.285-l33 X 1/1967 Crews 285133 X 6/1967 Henderson 175215 X 6/1969 Price166.5

FOREIGN PATENTS 8/ 1962 France. 5/ 1965 France.

THOMAS F. CALLAGHAN, Primary Examiner US. Cl. X.R.

